1. Field of the Invention
The present invention relates in general to auto-stereoscopic viewing systems for use in conjunction with flat panel displays. More particularly, the invention relates to a system for viewing anaglyphic imagery without the use of spectacles, which can be used concurrently by one or more viewers to experience the perception of depth.
2. Description of the Prior Art
Existing stereoscopic display systems using binocular parallax information are mainly categorized into two groups. In the first group, stereoscopic vision is achieved using a pair of special spectacles, e.g., polarizing spectacles, LC shutter spectacles, or anaglyphic spectacles, whereas in the second group, stereoscopic vision is achieved using a specific optical member, e.g., a lenticular lens or parallax barrier, arranged in front of a display or inside a display. In the second group, an observer can observe stereoscopic still or motion pictures without the need for special spectacles.
An anaglyph is a composite image that includes a pair of images taken from two slightly different angles. One of each pair of images is filtered to remove one of the three primary colors (e.g., red), and the other of each pair of images is filtered to remove the opposite two of the three primary colors (e.g., both green and blue). The two filtered images are superimposed on each other, and they are viewed with a red filter over one eye and a complementary-colored filter, either blue or green, over the other eye. This filtration causes a vectoring of discrete image information to go to each eye and pass into the visual center of the brain, for processing into a virtual stereoscopic image.
The use of color filters in the form of ‘anaglyph’ spectacles is well known in the art of stereoscopy and represents one of the most common examples of the use of spectacles to see stereoscopically. Two images of a stereo pair are typically combined into one single image; one of the images is generally red in color, and the other generally blue or green. The viewer then wears filter spectacles, such that one eye will see the red image and the other the blue or green image. If these images are appropriate right and left images, then three-dimensional stereoscopic vision results.
This traditional arrangement has the inherent disadvantage that the use of a single filter color for each eye causes the perceived image, although three-dimensional, to have very little, if any, residual color information. It sometimes is possible to see some color on traditional anaglyph images; however, the amount of color is severely limited and the perceived images are largely seen as being monochromatic.
In recent years, full color anaglyphic images have been realized through the use of red/cyan spectacles. One of the images is red in color (as in the traditional arrangement), but the other image includes both blue and green. According to commonly accepted theories of additive color synthesis, mixing the primary colors blue and green will create the color cyan. Similarly, a cyan gel filter will transmit mainly the blue and green spectrum of visible light, while blocking most of the red spectrum. This effect is being exploited in modern anaglyphic arrangements by allowing a vectoring of discrete image information to go to each eye and pass into the visual center of the brain, for processing into a virtual stereoscopic full-color image.
Both traditional and modern full-color anaglyphic arrangements have the disadvantage of requiring the use of special spectacles. In most cases, simple filters are placed in front of the viewer's eyes, or paper-framed spectacles are placed over the viewer's prescription spectacles. This has the unintended consequence of causing a subtle negative focus shift, in effect, introducing the symptoms of far-sightedness. Particularly in the case of a computer screen, at less than a meter normal spacing, the viewer typically experiences eyestrain when using gel filter spectacles. In fact, the red-filtered image is noticeably out of focus in most cases, due to the focus accommodation limits of all but the most youthful viewers. Plastic-mounted filters have the same poor performance as paper-framed spectacles.
Another inherent disadvantage of anaglyphic spectacles is that color gel filters are incapable of separating the two images perfectly, thus producing “crosstalk,” which has the appearance of ghost images in the scene. The main advantage of these spectacles is that they are inexpensive and even can be constructed at home using the appropriate color filters. Further, the art of creating anaglyphic images is widely known and quite simple, and it is even possible to produce anaglyphs from conventional two-dimensional images by adding depth cues with any modern paint program.
The symptoms arising from the use of conventional anaglyph viewing filters are numerous and well known. In many cases, after a short period of time, the use of anaglyph lenses can cause fatigue and, in some cases, even dizziness. Sometimes, users of these filters who view an anaglyph will complain of optical distortion. Some viewers also will complain of discomfort from the use of anaglyph gel filters. These complaints have caused this type of stereographic technology to be considered by many as second rate, despite its ease of use.
Anaglyphic stereoscopic viewing is a technology that has been in use for well over 100 years. For some of that time, particularly in the 1950's and early 1960's, in the United States, anaglyphic viewing for purposes of amusement, such as in books and movie theaters, had become quite popular. In these anaglyph stereoscopic viewing media, the conventional red and blue filters were mounted in a frame for wearing as a pair of spectacles. The viewer could then view the anaglyph to perceive a three dimensional image. However, the technology of anaglyph viewing has not really been advanced beyond the stage of amusement and novelty-type viewing. Recent attempts to encourage the use of anaglyphic spectacles in the viewing of cinematographic projections have proven unsuccessful. The benefits of stereoscopic viewing apparently are insufficient to overcome the drawbacks of distortion and the inconvenience of wearing anaglyphic filters.
The use of anaglyphic gel spectacles to view anaglyphic images or prints, therefore, has generally been limited to novelty items, largely due to optical distortions, poor optical quality, and poor color rendition. However, it has been recognized that, if the limitations of anaglyphic spectacles could be overcome, anaglyphic imagery could be elevated from a novelty item to a very useful art with numerous scientific and commercial applications.
It should, therefore, be appreciated that there remains a need for a system for anaglyic stereoscopic viewing that avoids the problems associated with anaglyphic gel spectacles. The present invention fulfills this need and provides further related advantages.